....said somebody somewhere who has never seen me in action: I'm plenty well versed with the former, not so familiar with the latter, but we live in hope.
What did you make of my "Plan B" exhaust? My gut feeling is it's not total rubbish, but it's never going to be the crowning glory either. That's ok, it's still a nice light system and if it works on the dyno then horsepower negates a multitude of sins: if there was a Tinder app for exhausts it would be the equivalent of an ugly bloke with lots of money.
So I just kept a casual eye out for a possible "Plan A" system, something that worked on a visual as well as practical level.
Eventually the glimmer of an alternative rose from the financial mire with somebody selling an incomplete “kinda-sorta-almost-but-not-quite” 999RS replica system.
It was in pretty poor shape to be honest, with a lot of surface corrosion (4 years sitting on a shelf after UK salt-laden roads) and a newer horizontal leg bodged up with a flexible concertina section incorporated…workable, but bloody ugly. And the section comprising the merge collector from both cylinders up into the tail pipe was completely missing in action.
Positives? It was still a Corse-size 63.5mm system; with an RS-style muffler (the only part in good nick), manifolds, and nicely made muffler splitter; and all the above negatives meant I could actually afford it.
(apologies, "phone-gate" means I don't have original as-found pics))
”Nicely made”? In general arrangement it was “Corse-ish” given the dimensions and style…but in construction nothing like it at all: someone had gone to a huge amount of trouble to handcraft the “tube” from 1.0mm stainless flat sheet, then fabricate the bends from pie-cut sections of the fabricated tube…it wasn’t/isn’t beautiful but you have to admire the effort that’s gone into it. Most 304 stainless tube is 1.6mm wall thickness (WT),1.2mm WT is available if you hunt around, so to make this 1.0mm WT is quite some dedication to making the system as light as possible.
Given all the the surface corrosion, Delboy's "Harpic Power Plus 10X" stainless steel cleaning hack seemed well worth a try:
Only to find that particular variation of Harpic is unavailable down here in Oz....bugger. But a quick Google told me the active constituent is Hydrochloric Acid and I just happened to have some HCl on hand for some concrete etching....and yup, it worked a treat. A quick buff with the wire-wheel afterwards and these were the usable bits I was left with, everything else being either too bodgy, too beat up, or simply missing (speaking of missing, I forgot to include the mandrel bend elbow out of the horizontal cylinder that I'd be using) :
First task in mocking things up was to somehow mount the "RS" muffler with the road subframe.
For reference, this is Leon Haslam's "Airwaves" BSB 999F06, with the Corse/RS rear subframe and muffler mounting arrangement completely different to the 749R/RS-kit system:
So you'll see in my parts photo (a few pic's back) I've machined a threaded alloy block which the muffler strap tightens against, giving the required central mounting point. Next, the lower subframe cross brace was exactly where the muffler inlets needed to be, so that had to go. Nearly there, but the rear edge of the muffler clashed with the gusseting at the subframe bend, so they got a wee haircut such that the muffler didn't hang out the back like the gang plank on a pirate ship. Eventually I arrived at this:
So it's job done, eh? Nup. The RS muffler shroud doesn't just sit over the muffler, it wraps around it, partially encapsulating it. This is where the thickness of the road subframe tube becomes a pain in the klacker, making it difficult to centralise the muffler within the full RS shroud as the tail sits too high in relation.
Up until this this point I'd just used a simple alloy strap across the subframe to mount the tail with dzus clips either end. This simply replicated the 749R arrangement with its Leo Vince exhaust and RS tail: it's not fancy but weighs bugger all and gets the job done. But the tail just wouldn't quite snug down far enough to not bug the shit out of me, and no amount of swearing was going to find me the 10mm I needed.
An online buddy had made some exquisite billet versions (lovely work JJ!) of the Factory 749R "RS kit" tail mounting clips seen here with an oh-so-sexy super-rare Akrapovic exhaust (insert school girl swoon here):
Now I don't have anything like JJ's skills but some billet aluminium was sourced and I had a crack at making a "high street" version of JJ's Versace tail clips:
I'm sure JJ was laughing when I mentioned them because he knew exactly what fiddly lil' fucker's they are to make. Virtually no right angled or parallel surfaces and some truly weird angles, my limited intellectual bandwidth was fully tested!
But they gave me the room I needed, compared here against the original strap method:
So much faffing around for so little effect:
Time for a deep breath, some dutch courage/beer and off we go on the actual exhaust making....
The original tube sections were hand-built for a very good reason: you just can't find 1.0mm WT 63.5mm (2 1/2") 304 stainless tube. There are some folks who will make the tube for you, or you can go for a more exotic 321 stainless option over el-cheapo 304 (321 is better in high temperature situations, better ductility and resistance to stress fracture means they can make it thinner for the same application) but the cost is prohibitive, especially with shipping down to Oz, you might as well just buy a genuine RS exhaust.
1.6mm WT tube is very common, 1.2mm less so, but I managed to get my grubby mits on 2 x 1m lengths....no pressure, but don't fuck this up, bro'!
The merge collector joining the horizontal/vertical tubes was a lil' problematic. You basically have a choice between nice flowing units that take up a lot of real estate or compact units which don't flow as well. I'd ordered the former but once I started offering up the tube and mocking things up I reluctantly had to go with the latter (note the outlet length is irrelevant here, it'll be cut off). No, there won't be a smiley-face stamp for picking which is the most expensive:
As for the major bends, I was struggling to find appropriate short radius mandrel bends so I was going with some beautifully fabricated "Tigtonic" pre-made pie-cut units which I would cut to suit. Unfortunately no-one does anything thinner wall than 1.6mm so there was no decision to be made on that front:
So my plan was to mock it up, tack it together, then enlist a pro' to TIG weld it "proper like". So this is what emerged from my fevered imagination:
I was really hoping to get a word of mouth recommendation for an "aesthetic" TIG welder, only nothing was really forthcoming. But jumping online I found a guy with some great reviews and impressive photo's of his work. We spoke about the job, he seemed keen and I left the tacked up tube sections with him...
....things took a bit longer than expected as he wanted to re-do some welds, all good, he's obviously a perfectionist, right? Time came to pick it up and he mumbled something about only charging half price (still not an insignificant sum, there are more than a few man-hours in it) and it was pretty obvious why: sure the welds were strong and technically adequate, but there was nothing aesthetically pleasing about them. I wasn't expecting the robotic perfection of the "Tigtonic" bends, but even the "Plan B" exhaust welds shaded these.
(Again, pictures would be worth these 1000 words but they're gone with my smashed phone....AAAARGH!)
I was stuck in no-man's land and couldn't see any other option than to try and "dress" the welds to invisibility. The trouble is once you start dressing the thin material it becomes even thinner, and occasionally defects need some touch up welding. (cue the scary "Jaws" music...) Yup, holes are then blown in that paper-thin material. As we know welding relies on a pool of molten metal, which then shrinks on cooling, distorting the tube. Bottom line? What had been just a tad ugly was now pretty much rooted: no good deed goes unpunished.
In truth, I could have cut out the offending tubes, but decided to basically start again. Yes, dear reader you (and I) have come all this way for nothing.....(sigh).
